Pollution by malodor, deleterious materials in the air, etc. has become a problem in recent years. Also, water pollution by domestic waste water, industrial waste water, etc. has spread widely. Thus, environmental pollution has become a serious social problem.
In removing malodor or deleterious materials, absorption process using acid or alkali, and adsorption process using an adsorbent have been employed conventionally. In these processes, however, it is necessary to treat a waste liquid or spent adsorber. On the other hand, it is known that when a semiconductor device is irradiated with light, electrons having strong reducing action and holes having strong oxidizing action are formed and the molecular species after having been in contact with the semiconductor device are decomposed by oxidation-reduction action. Such a photocatalytic action of the semiconductor is applicable to decomposition and removal of deleterious materials.
JP-B-9850/1990 discloses to decompose deleterious materials in waste by using a photocatalyst such as titanium oxide. JP-B-78326/1992 discloses to eliminate toilet night soil odor, tobacco odor, etc. by using a photocatalyst such as titanium oxide.
In addition, a number of titanium oxide photocatalysts are disclosed in JP-A-199524/1994, 205974/1994, 279026/1994, 819/1995, 241475/1995, 275704/1995, 303835/1995, 99041/1996, 81222/1996, 126845/1996, and 182934/1996.
JP-A-131834/1996 discloses a titanium oxide sol for photocatalyst and a multifunctional material having photocatalytic action.
The above conventional titanium oxide photocatalysts are, however, ones which employ titanium oxide, e.g., anatase-type titanium oxide, rutile-type titanium oxide, brookite-type titanium oxide, amorphous titanium oxide, metatitanic acid and orthotitanic acid, titanium hydroxide, or hydrate titanium oxide. It has been therefore demanded a novel photocatalyst having superior activity and a multifunctional material using the same.
Accordingly, it is an object of the invention to provide a novel photocatalyst having superior activity, a process thereof, and a multifunctional material using the same.